Embodied virtual hands intensify kinesthetic illusion and are associated with spontaneous muscle activity: A sEMG study

Visually induced kinesthetic illusion (V-KI) - the sensation of movement without actual limb motion - has been shown to enhance brain activity related to voluntary movement and to modulate descending volleys at the spinal level. In this study, we sought to determine whether these effects extend to peripheral muscles and whether the magnitude of this response depends on the strength of virtual body embodiment. Twenty-six healthy participants observed videos of their own hand performing wrist movements under conditions that manipulated spatial alignment and included a single tactile-priming session administered before movement observation. Surface electromyography (sEMG) was recorded from the extensor carpi ulnaris and flexor carpi radialis during V-KI. Tactile priming increased both ownership ratings and illusion intensity. In contrast, condition-level differences in sEMG were modest and not consistently observed across all comparisons. Generalized linear mixed model analysis revealed that sEMG activity was predicted by illusion intensity, with an additional main effect of tactile priming. These findings suggest that V-KI is associated with peripheral muscle activity, and that this effect is closely linked to the intensity of the kinesthetic illusion.